The present invention relates to wireless data communication networks and more particularly to such a network which employs mobile wireless stations and which will automatically organize itself for efficient operation.
While it has previously been proposed to arrange wireless data communications stations in a hierarchical network, such systems have typically contemplated that the network backbone i.e., the gateway stations and channels which implement longer distance links, will typically be essentially pre-selected or predetermined even though non-gateway stations may switch affiliation or principal contact from one gateway or cell-base to another. Further, the gateway stations are typically immobile or stationary. For example, in cellular telephone networks there can be a hand-off of a mobile unit from one base station to another, the hand-off being initiated by the base station.
There are, however, situations in which it is disadvantageous to have to pre-determine or pre-select what stations are going to function as backbone gateways. Examples of such situations are military battlefield operations where deployment of facilities may be changed rapidly and erratically and a gateway station may be lost unpredictably. In the civilian context, disaster relief operations may also need to deploy equipment quickly and it is desirable that effective and pervasive communications be made easily available without having to promulgate a network structure from a central command post or authority. As will also be understood, it is highly desirable that it not be necessary to provide a variety of different equipment configurations or capabilities. Rather, it is preferable that a single standard operational configuration be usable at all stations in a flexible network.
Among the several objects of the present invention may be noted that the provision of a mobile radio communications network in which a plurality of mobile stations will automatically organize themselves into a hierarchical network in which some of the stations operate as message gateways for a cluster of stations, thereby forming a network backbone; the provision of such a network which employs a plurality of stations which are essentially similar to each other; the provision of such a network in which the cluster gateways operate at a relatively high power level to provide longer distance network links; the provision of such a network in which unneeded redundancy of channels is avoided; the provision of such a network which possesses the ability to adaptively reorganize in the face of movement or destruction of cluster gateways; the provision of such a network which is highly reliable, which is easily implemented and which is of relatively simple and inexpensive construction. Other objects and features will be in part apparent and in part pointed out hereinafter.
A mobile radio communications network of the present invention employs a plurality of similar mobile stations each of which can transmit on either a relatively high power level or a relatively low power level. The invention employs a method of operating each station so as to automatically organize a group of stations into a multi-layered network for relaying messages from station to station with some of the stations operating at the relatively high power level as message gateways for a cluster of other stations, thereby to form a network backbone. In accordance with the method, each station attempts initially to establish an affiliation link at the lower power level to an existing gateway. If that attempt does not succeed within a randomly determined length of time, the station switches to the higher power level and commences operation as a cluster gateway. Data which identifies the other stations affiliating with each cluster gateway is communicated between the cluster gateways. Preferably, each cluster gateway periodically determines if any other cluster gateway is within affiliation range and, if so, initiates a procedure which terminates cluster gateway status of the respective station if that termination will not reduce connectivity of the network backbone below a preselected level.